The present invention relates to a ribbon cartridge for a typewriter having a correction key.
It is known that typewriters having a correction key are provided with two independent ribbons, one for the typewriting and one for the cancellation, which is obtained by enabling the machine by means of the correction key and then pressing the key corresponding to the erroneously typed symbol. In the majority of cases the typewriter ribbon is of the synthetic plastics film type and therefore typing is effected by depositing a portion of this plastics film on the sheet to be typed, by the operation of the type bars on which the various symbols are engraved, which press the plastics film against the sheet to by typed leaving a portion which remains adhering to the sheet. Cancellation is effected with correction ribbons having adhesive properties in relation to these plastics films and which therefore achieve separation of the incorrect symbol from the sheet being typed by causing it to adhere to its adhesive surface. In known constructions the typewriter ribbon and correction ribbon are made separately and are mounted on the typewriter independently from one another. In particular, the typewriter ribbons are contained in suitable sealed typewriter ribbon cartridges whilst the correction ribbons are directly mounted by an operator onto the typewriter and are replaced periodically or when worn out.
The arrangement described is not free from disadvantages. In particular, each type of plastics film typewriter ribbon requires a particular correction ribbon which does not work (or works poorly) with typewriter ribbons of different type. Since correction ribbon and typewriter ribbon are produced, sold and mounted separately it is often not possible to provide the appropriate correction ribbon for the particular typewriter ribbon utilised, and therefore the possibility of a simple correction of a typing error offered by a machine with a correction key is entirely or partly lost. Moreover the fitting and/or replacement of the correction ribbon, which does not have a modular cartridge, is often complex and difficult and sometimes also requires the removal of the typewriter ribbon cartridge. Finally, if the typewriter ribbon is replaced with a ribbon of different type it is necessary also to replace the correction ribbon thereby performing a further operation.